To improve fitness, what must one do according to the overload principle?

The overload principle is a fundamental concept in fitness training that states in order to improve physical fitness, one must increase the demands placed on the body. This can be accomplished by increasing the intensity, duration, or frequency of exercise. By doing so, the body adapts to the increased workload, leading to improvements in strength, endurance, and overall fitness.

When intensity is increased, for example through lifting heavier weights or running at a faster pace, the body responds by building muscle or enhancing cardiovascular capacity. Similarly, increasing the duration of a workout can improve endurance, while adding more sessions per week can help to build a consistent routine that promotes further adaptations.

In contrast, reducing workout duration or maintaining the same intensity over time does not stimulate adaptation and could lead to plateaus in fitness levels. Focusing solely on diet, while important, neglects the critical role that physical activity plays in fitness improvement. Therefore, to effectively leverage the overload principle for enhanced fitness outcomes, one must adjust the workload by increasing intensity, duration, or frequency of exercise.